The present invention relates to a method of spinning and crimping a multifilament yarn, as well as an apparatus for carrying out the method.
To produce a crimped yarn, it is known to extrude by means of a spinning apparatus from a thermoplastic melt a filament bundle consisting of a plurality of strandlike filaments. After a cooling, the filament bundle is crimped by means of a crimping unit. In this process, the individual filaments of the bundle are deformed to loops and coils, so that the yarn formed from the filament bundle exhibits a crimp. To achieve such a deformation of the filaments in the filament bundle, the crimping unit may be designed and constructed, for example, as a texturing nozzle, wherein the filament bundle is compressed to a yarn plug by means of a conveying medium. Thus, when the filament bundle impacts upon the yarn plug, the desired loops and coils of the individual filaments will take shape. To realize an as stable crimp as possible, the filament bundle is advanced through a heated conveying medium and simultaneously heated, so that a plastic deformation is allowed to occur in the individual filaments of the bundle. After cooling the yarn plug, same is transformed by withdrawing into a crimped yarn, which is subsequently wound to a package.
In its intensity and stability, the crimp of the yarn is decisively influenced by the deformation of the individual filaments, i.e., with the use of a texturing nozzle, by the plug formation, and by the heat treatment of the yarn plug. Thus, the parameters, which decisively influence the crimp results, are not only temperature and pressure of the conveying medium, but also the dwelling time of the yarn plug during the heat treatment.
For example, DE 196 13 177 discloses a method and an apparatus, wherein the filaments of the filament bundle having been converted to a yarn plug, advance through an extremely long cooling zone before being disentangled to the crimped yarn. However, this method basically involves the problem that a larger number of individual filaments within the bundle does not guarantee a uniform treatment both in the formation of loops and coils and in the heating and cooling of all filaments of the bundle.
It is therefore an object of the invention to provide a method and an apparatus for spinning and crimping a multifilament yarn, which enable the production of a qualitatively superior crimped yarn with a stable and uniform crimp of the filaments.
In accordance with the invention, the above and other objects and advantages are accomplished in that before crimping, the filament bundle is divided into a plurality of bundle components, with each bundle component being separately crimped. After crimping, the bundle components are combined to form a multifilament yarn.
The invention was not suggested either by the methods and apparatus disclosed in EP 0 861 931 and EP 0 784 109, since the known methods and apparatus relate exclusively to the production of a composite yarn from a plurality of individual yarns. Each of the individual yarns differs in its polymer, its color, and/or its treatment, with each individual yarn being produced from respectively one filament bundle. Each filament bundle receives an individual treatment. In comparison therewith, the method and apparatus of the present invention are directed to producing a yarn from a filament bundle of a single-colored polymer melt. In this connection, the invention distinguishes itself in particular in that the crimped yarn receives a high crimp level, which is increased by at least 10% in comparison with conventionally crimped yarns. As a result of dividing the filament bundle into a plurality of bundle components, the individual filaments undergo a particularly intensive treatment during the crimping process. The high crimp level produces a particularly great bulkiness of the yarns, which does extremely well in yarns for making carpets.
To ensure a uniform treatment of all individual filaments of the filament bundle, it is preferred to have approximately the same number of filaments in each bundle component, and to crimp each bundle component under substantially identical conditions.
The further development of the invention, wherein a texturing nozzle is used for crimping, distinguishes itself in that the dwelling time for treating the yarn plug is substantially increased without reducing the spinning speed.
In particular, during the cooling of the yarn plug, it is thus possible to realize even in a short cooling zone an intensive cooling, which ensures an adequately low temperature of the individual filaments, when the yarn plug is disentangled. With that, the loops and coils set in the individual filaments are maintained even at very high withdrawing speeds.
However, in the production of the crimped yarn, there is also the possibility of pretreating the bundle components at least in one step after cooling and before crimping. The pretreatment may be realized on the bundle components, for example, by an entanglement or false twist. In so doing, however, it is important that each bundle component be pretreated under identical conditions.
It would likewise be possible to subject the bundle components to at least one aftertreatment after crimping and before combining them. Likewise in this instance, the aftertreatment is performed under identical conditions, so that the filament strands of the crimped yarn exhibit largely identical properties.
The division of the filament bundle may occur both after cooling and before cooling the filament bundle. In the latter case, the division of the filament bundle is realized by a partition inside the spinneret. However, to partition the spinneret, it would also be possible to provide two spinnerets arranged in direct side-by-side relationship, with each spinneret receiving a melt of a polymer.
To combine after crimping the individual filaments of the bundle components to the crimped yarn, a further advantageous development of the invention proposes to combine the bundle components to the yarn by an entanglement. This allows to achieve a high yarn cohesion at the same time.
For carrying out the method, an apparatus is proposed wherein the extruded filament bundle is divided into a plurality of bundle components by a separating means, which extends in the path of the yarn upstream of the crimping unit. The crimping unit is composed of a plurality of identical texturing means, with one of the texturing means being associated to each bundle component. To join the bundle components to form the crimped yarn, a combining means is provided between the crimping unit and the takeup unit.
The separating means may be formed by a plurality of yarn guides, which are arranged inside the cooling device or between the cooling device and crimping unit. However, it is also possible to form the separating means by a partition, which extends inside the spinning unit.
As texturing means, it is preferred to use texturing nozzles, in which the bundle component advances via a conveying channel to a stuffer box. In the stuffer box, the filaments are compressed to a yarn plug. As a result of dividing the filament bundle, it is accomplished that the reduced number of the individual filaments makes it possible to realize a higher level of loop and coil formation within the yarn plug.
Since it is preferred to use heated conveying fluid in the texturing nozzle for forming the yarn plug, it is possible to advance the yarn plug for cooling on the circumference of a cooling drum. Such cooling drums include a radial cooling air stream, which penetrates the yarn plug lying against the circumference of the cooling drum for purposes of cooling it. This allows to accomplish a uniform and intensive cooling of all yarn plugs extending parallel on the circumference of the cooling drum, until the disentanglement point is reached.
It is preferred to use as combining means an entanglement nozzle, which advances the bundle components jointly in a yarn channel, to which an air jet is supplied in such a manner that the individual filaments of the bundle components intertwine.
The invention is not limited either to the individual treatment steps or to the named treatment means, since what is essential for the method includes both the division into bundle components and their equal treatment during the crimping, as well as the combination of all filaments to a yarn.